Fuel cell unit, composite block of fuel cells and method for manufacturing a composite block of fuel cells

ABSTRACT

In order to create a fuel cell unit, comprising a cathode-anode-electrolyte unit and a contact plate which is in electrically conductive contact with the cathode-anode-electrolyte unit, which requires only small production resources and is thus suitable for large-scale production it is suggested that the fuel cell unit comprise a fluid guiding element which is connected to the contact plate in a fluid-tight manner, forms a boundary of a fluid chamber having fluid flowing through it during operation of the fuel cell unit and is designed as a shaped sheet metal part.

[0001] The present invention relates to a fuel cell unit which comprisesa cathode-anode-electrolyte unit and a contact plate which is inelectrically conductive contact with the cathode-anode-electrolyte unit(CAE unit).

[0002] Fuel cell units of this type are known from the state of the art.

[0003] As a rule, several such fuel cell units are combined to form acomposite block of fuel cells, in which the fuel cell units follow oneanother along a stacking direction.

[0004] In the cathode-anode-electrolyte unit, an electrochemicalreaction takes place during the operation of the fuel cell unit, duringthe course of which electrons are supplied to the anode of the CAE unitand electrons withdrawn from the cathode of the CAE unit for theionization of oxygen atoms. The contact plates arranged between the CAEunits of two consecutive fuel cell units serve to balance the chargebetween the cathode of the one fuel cell unit and the anode of theadjacent fuel cell unit in order to supply the cathode with theelectrons required for the ionization. Electric charges may be tappedfrom the edge-side contact plates of the composite block of fuel cellsin order to supply them to an external useful current circuit.

[0005] The contact plates used with the known fuel cell units are metalplates which are milled or eroded from the entire plate and betweenwhich the CAE units are inserted so that these contact plates serve atthe same time to hold the CAE units, as well. Furthermore, these platesare provided with channels which serve for the passage of fluids(combustible gas, oxidation agent and/or refrigerant) through the fuelcell unit.

[0006] These known fuel cell units are very complicated to produce andthus suitable only for small quantities.

[0007] The object underlying the present invention is therefore tocreate a fuel cell unit of the type specified at the outset whichrequires only small production resources and is thus suitable forlarge-scale production.

[0008] This object is accomplished in accordance with the invention, ina fuel cell unit with the features of the preamble to claim 1, in thatthe fuel cell unit comprises a fluid guiding element which is connectedto the contact plate in a fluid-tight manner, forms a boundary of afluid chamber having fluid flowing through it during operation of thefuel cell unit and is designed as a shaped sheet metal part.

[0009] Such a shaped sheet metal part may be produced from anessentially flat sheet metal blank by means of one or more shapingprocesses, in particular, by means of embossing and/or deep drawing.These production methods are considerably more suitable and moreinexpensive for a large-scale production than the production of solidmetal plates by way of milling or erosion.

[0010] In addition, it is possible to save on material and weight due tothe use of shaped sheet metal parts.

[0011] The fluid flowing through the fluid chamber can be a combustiblegas, an oxidation agent or a refrigerant.

[0012] In particular, it may be provided for the fluid chamber to besurrounded, apart from by the fluid guiding element, by the contactplate and by the cathode-anode-electrolyte unit.

[0013] In a preferred configuration of the invention it is provided forthe cathode-anode-electrolyte unit of the fuel cell unit to be arrangedon the fluid guiding element.

[0014] In particular, it may be provided for thecathode-anode-electrolyte unit to be arranged between the fluid guidingelement, on the one hand, and the contact plate of the same fuel cellunit or an adjacent fuel cell unit, on the other hand.

[0015] The inventive fuel cell unit is already particularly simple tohandle prior to the assembly of the composite block of fuel cells whenthe cathode-anode-electrolyte unit is held between the fluid guidingelement and the contact plate of the same fuel cell unit.

[0016] Alternatively hereto, it may also be provided for thecathode-anode-electrolyte unit to be designed as a coating on the fluidguiding element or on the contact plate of the fuel cell unit.

[0017] It is particularly favorable when not only the fluid guidingelement but also the contact plate is designed as a shaped sheet metalpart. In this case, the contact plate of the fuel cell unit may also beproduced in a simple manner by way of embossing and/or deep drawing froman essentially flat sheet metal blank which is more suitable and moreinexpensive for a large-scale production than the production of solidcontact plates by way of milling or erosion.

[0018] The contact plate and the fluid guiding element may, in thiscase, form a two-part shell of the fuel cell unit which surrounds thecathode-anode-electrolyte unit.

[0019] The inventive construction of a fuel cell unit is particularlysuitable for so-called high-temperature fuel cell units which have anoperating temperature of up to 950° C. and can be operated, without anyexternal reformer, directly with a hydrocarbonaceous combustible gas,such as, for example, methane or natural gas or alternatively hereto,using an external reformer, with a diesel or petroleum motor fuel.

[0020] For use in such a high-temperature fuel cell unit the shapedsheet metal parts, from which the fluid guiding element and also, whereapplicable, the contact plate of the fuel cell unit are formed, areproduced from a sheet metal material which is chemically resistant atthe resulting temperatures of up to 950° C. in relation to thecomponents of the combustible gas, the combustion air supplied and arefrigerant supplied where applicable (for example cooling air).

[0021] High-grade steel sheets resistant to high temperatures or steelsheets coated with an inorganic or ceramic material are particularlysuitable for this purpose.

[0022] Furthermore, a sheet metal material is preferably selected whichhas a thermal coefficient of expansion compatible with that of the CAEunit.

[0023] The thickness of the sheet metal material used is preferably atthe most approximately 3 mm, in particular, at the most approximately 1mm.

[0024] In order to achieve a reliable connection between the contactplate and the fluid guiding element of the same fuel cell unit which isalso resistant and gas-tight at high temperatures, it is preferablyprovided for the fluid guiding element and the contact plate to beconnected to one another by way of welding, preferably by laser weldingor by electron beam welding.

[0025] Alternatively or in addition hereto it may be provided for thefluid guiding element and the contact plate to be connected to oneanother by way of soldering, preferably by hard soldering.

[0026] In order to make the required compensation of charges between theCAE units of fuel cell units adjacent to one another possible in asimple manner it is provided in a preferred configuration of theinventive fuel cell unit for the fluid guiding element to have anopening for the passage of contact elements (e.g. of an adjacent fuelcell unit) to the cathode-anode-electrolyte unit.

[0027] In order to be able to hold the CAE unit between the fluidguiding element and the contact element of the fuel cell unit withoutshorting the anode and the cathode of the same fuel cell unit with oneanother, it is advantageously provided for the fluid guiding element toabut on the cathode-anode-electrolyte unit via an electricallyinsulating seal.

[0028] In a preferred configuration of the invention, the fluid guidingelement is designed as a fluid guiding frame which abuts on thecathode-anode-electrolyte unit along the entire edge thereof via theelectrically insulating seal.

[0029] It is particularly favorable when the seal between the fluidguiding element and the CAE unit comprises mica.

[0030] Alternatively or in addition hereto, it may be provided for theseal between the CAE unit and the fluid guiding element to comprise aflat seal.

[0031] Alternatively or in addition hereto, it may be provided for theseal between the CAE unit and the fluid guiding element to comprise acoating on the fluid guiding element and/or on thecathode-anode-electrolyte unit.

[0032] Such a coating may be applied, for example, by the screenprinting method, by roller coating or by spray coating onto the fluidguiding element or the cathode-anode-electrolyte unit.

[0033] Inorganic or ceramic sealing media, which are chemicallyresistant, gas-tight and electrically insulating at an operatingtemperature of up to 950° C., can be considered, in particular, for thesealing.

[0034] A solder glass can, for example, be used as sealing medium andthis can be composed, for example, like a solder glass known from EP 0907 215 A1, i.e. can contain 11 to 13% by weight of aluminum oxide(Al₂O₃), 10 to 14% by weight of boron oxide (BO₂), approximately 5% byweight of calcium oxide (CaO), 23 to 26% by weight of barium oxide (BaO)and approximately 50% by weight of silicon oxide (SiO₂).

[0035] Furthermore, it may be provided for the seal between the CAE unitand the fluid guiding element to be designed as a movable seal (slidefit sealing).

[0036] Furthermore, it may be provided for the fluid guiding element tobe connected to the CAE unit by way of flanging.

[0037] It may, in particular, be provided for a flange fold areaengaging around the CAE unit to be formed on the fluid guiding element.

[0038] In order to obtain the required pressing force for the sealingbetween the CAE unit and the fluid guiding element irrespective of anyexternal biasing of the fuel cell units against one another, it ispreferably provided for the cathode-anode-electrolyte unit and the fluidguiding element to already be biased elastically against one another onaccount of the geometry of the fuel cell unit and the connection betweenthe fluid guiding element and the contact plate of the fuel cell unit.

[0039] In order to be able to use the fluid guiding element, apart fromfor holding the CAE unit, also for the formation of fluid channels,through which a fluid is supplied to the fuel cell unit or dischargedfrom the same, it is provided in a preferred configuration of theinvention for the fluid guiding element to be provided with at least onefluid port.

[0040] The area of the fluid guiding element surrounding the fluid portserves in this case as fluid guiding area of the fluid guiding element.A fluid channel then results from the fluid guiding areas of the fluidguiding elements of fuel cell units following one another in thestacking direction.

[0041] The fluid supplied or discharged via the fluid channel can be anoxidation agent or, preferably, a combustible gas.

[0042] It is particularly favorable when the holding means is providedwith a fluid supply channel opening and with a fluid discharge channelopening. In this case, the fluid guiding element can be used not onlyfor the formation of a fluid supply channel but also for the formationof a fluid discharge channel.

[0043] In order, during the formation of such fluid channels, tomaintain the required electric insulation between the contact plates andfluid guiding elements of adjacent fuel cell units, it is advantageouslyprovided for the fuel cell unit to comprise an electrically insulatingfluid channel seal, via which the contact plate of the fuel cell unitabuts on the fluid guiding element of an adjacent fuel cell unit.

[0044] Alternatively or in addition hereto it may also be provided forthe fuel cell unit to comprise a fluid channel seal, via which the fluidguiding element of the fuel cell unit abuts on the contact plate of anadjacent fuel cell unit.

[0045] Such a fluid channel seal may, for example, comprise a coating onthe fluid guiding element and/or on the contact plate.

[0046] Such a coating may be applied, in particular, by the screenprinting method, by roller coating or spray coating onto the fluidguiding element or the contact plate, respectively.

[0047] Inorganic and ceramic materials, which are chemically resistant,gas-tight and electrically insulating at the resulting operatingtemperatures of up to 950° C., can be considered, in particular, assealing media.

[0048] A particularly simple construction of the fluid channel sealresults when this comprises a flat seal.

[0049] Particularly when the holding plate and the contact plate areconnected to one another by flanging, it is of advantage when the fluidchannel seal comprises at least two separate sealing elements which canbe arranged, in particular, in different planes.

[0050] In order to compensate for different heat expansions, it isparticularly favorable when the fluid channel seal comprises a slide fitsealing.

[0051] Particularly with a design as slide fit sealing it is ofadvantage when the fluid channel seal comprises a material, preferably asolder glass, viscous at the operating temperature of the fuel cellunit.

[0052] Claim 20 is directed to a composite block of fuel cells whichcomprises a plurality of inventive fuel cell units which follow oneanother along a stacking direction.

[0053] In order to be able to fix the individual fuel cell units of thecomposite block of fuel cells in their position relative to one anotherand, where required, to be able to generate an adequate contact pressurefor the sealing between the CAE unit and the fluid guiding elementand/or for the sealing between the fluid guiding element and the contactplate of an adjacent fuel cell unit, it is favorable when the compositeblock of fuel cells comprises at least one clamping element for bracingthe fuel cell units against one another.

[0054] The composite block of fuel cells can, in particular, comprisetwo end plates which can be braced against one another by means of theclamping element.

[0055] In order to be able to supply a fluid (combustible gas, oxidationagent or refrigerant) to the composite block of fuel cells in a simplemanner or discharge the fluid out of the composite block of fuel cellsit is advantageously provided for at least one of the end plates to haveat least one fluid port.

[0056] Bracing of the fuel cell units of the composite block of fuelcells against one another by means of a separate clamping element issuperfluous when it is advantageously provided for the fluid guidingelement of at least one of the fuel cell units to be connected to thecontact plate of an adjacent fuel cell unit by way of flanging. Thisflanging is sufficient to secure the fuel cell units in their positionrelative to one another.

[0057] Nevertheless, an additional clamping element can be used in sucha case to generate the contact pressure between the CAE units and thecontact plates of the composite block of fuel cells.

[0058] It may, in particular, be provided for a flange fold areaengaging around the contact plate of the adjacent fuel cell unit to beformed on the fluid guiding element of at least one of the fuel cellunits.

[0059] Alternatively hereto, it may also be provided for a flange foldarea engaging around the fluid guiding element of the adjacent fuel cellunit to be formed on the contact plate of at least one of the fuel cellunits.

[0060] In a preferred configuration of the composite block of fuel cellsit is provided for an electrically insulating fluid channel seal to bearranged between the flange fold area and the contact plate of theadjacent fuel cell unit. As a result of the flanging, such a fluidchannel seal is already subject to the contact pressure required for anadequate sealing without any force of an external clamping system beingrequired for this purpose.

[0061] In order to produce a composite block of fuel cells whichcomprises a plurality of inventive fuel cell units, a method is suitablewhich comprises the following method steps:

[0062] Assembly of the individual fuel cell units by arranging acathode-anode-electrolyte unit between a contact plate and a fluidguiding element and gas-tight connection of the contact plate to thefluid guiding element;

[0063] subsequent assembly of the composite block of fuel cells byarranging a plurality of fuel cell units along a stacking direction andfixing the fuel cell units in their position relative to one another.

[0064] With such a method, the individual parts contact plate, CAE unitand fluid guiding element of a respective fuel cell unit are first ofall fitted together and the contact plate and the fluid guiding elementare connected to one another, for example, by welding or soldering inorder to assemble the individual fuel cell unit.

[0065] Subsequently, the assembly of the entire composite block of fuelcells takes place, with which the fuel cell units of the composite blockof fuel cells are preferably braced against one another by means of atleast one clamping element.

[0066] In a special configuration of the method it may be provided forthe fuel cell units of the composite block of fuel cells to be arrangedbetween two end plates and for the two end plates to be braced againstone another.

[0067] The method described above is suitable for the production of thecomposite block of fuel cells, in particular, when the fluid guidingelement of at least one fuel cell unit abuts on the contact plate of anadjacent fuel cell unit via a flat seal or a slide fit sealing.

[0068] If, on the other hand, in the composite block of fuel cells to beproduced the fluid guiding element of one fuel cell unit is connected tothe contact plate of an adjacent fuel cell unit by way of flanging, amethod which comprises the following method steps is particularlysuitable for the production of such a composite block of fuel cells:

[0069] Assembly of several fluid guiding element-contact plate units byconnecting a respective fluid guiding element of one fuel cell unit to acontact plate of an adjacent fuel cell unit by way of flanging;

[0070] formation of a stack consisting of fluid guiding element-contactplate units following one another along a stacking direction, whereinone respective cathode-anode-electrolyte unit is arranged between twosuch respective units;

[0071] gas-tight connection of the contact plates of the fuel cell unitsto the respective fluid guiding element of the same fuel cell unit.

[0072] With this method for the production of the composite block offuel cells, the fluid guiding element of a first fuel cell unit is firstof all preassembled with the contact plate of a second fuel cell unit byway of flanging, preferably at the combustible gas channel and at thedischarge gas channel, wherein electrically insulating fluid channelseals are integrated into the respective flangings. Subsequently, thefinal assembly of the composite block of fuel cells is carried out inthat the CAE units are arranged each time between the consecutive fluidguiding element-contact plate units and the contact plates and fluidguiding elements belonging to the same fuel cell unit, which hold arespective CAE unit between them, are connected to one another in agas-tight manner by way of welding or soldering.

[0073] Additional features and advantages of the invention are thesubject matter of the following description and drawings illustratingembodiments. In the drawings:

[0074]FIG. 1 shows a schematic perspective illustration of a fuel celldevice with supply lines and discharge lines for the oxidation agent andthe combustible gas;

[0075]FIG. 2 shows a schematic longitudinal section through a compositeblock of fuel cells arranged in the housing of the fuel cell device fromFIG. 1;

[0076]FIG. 3 shows a schematic longitudinal section through acathode-anode-electrolyte unit with contact plates adjoining thereto;

[0077]FIG. 4 shows a schematic perspective exploded illustration of twofuel cell units of the composite block of fuel cells from FIG. 2following one another in a stacking direction;

[0078]FIG. 5 shows a schematic plan view of a contact plate of one ofthe fuel cell units from FIG. 4;

[0079]FIG. 6 shows a schematic plan view of a fluid guiding frame of oneof the fuel cell units from FIG. 4;

[0080]FIG. 7 shows the right-hand part of a schematic cross sectionthrough three fuel cell units of the composite block of fuel cells fromFIG. 2 following one another in the stacking direction;

[0081]FIG. 8 shows the right-hand part of a schematic longitudinalsection through three fuel cell units of the composite block of fuelcells from FIG. 2 following one another along the stacking direction ina first embodiment of the composite block of fuel cells, with which afluid guiding frame of a fuel cell unit abuts via a flat seal on acathode-anode-electrolyte unit (CAE unit) of the same fuel cell unit andvia an additional flat seal on the contact plate of an adjacent fuelcell unit;

[0082]FIG. 9 shows a schematic longitudinal section corresponding toFIG. 8 through three fuel cell units following one another along thestacking direction in a second embodiment of the composite block of fuelcells, with which the fluid guiding frame of one fuel cell unit isconnected to the contact plate of an adjacent fuel cell unit by way offlanging;

[0083]FIG. 10 shows a schematic longitudinal section corresponding toFIG. 8 through three fuel cell units following one another along thestacking direction in a third embodiment of the composite block of fuelcells, with which the fluid guiding frame of one fuel cell unit isconnected to the CAE unit of the same fuel cell unit by way of flangingand to the contact plate of an adjacent fuel cell unit likewise byflanging;

[0084]FIG. 11 shows a schematic longitudinal section corresponding toFIG. 8 through three fuel cell units following one another along thestacking direction in a fourth embodiment of the composite block of fuelcells, with which the fluid guiding frame of one fuel cell unit isconnected to the contact plate of an adjacent fuel cell unit via a slidefit sealing; and

[0085]FIG. 12 shows a schematic longitudinal section corresponding toFIG. 8 through three fuel cell units following one another along thestacking direction in a fifth embodiment of the composite block of fuelcells, with which the fluid guiding frame of one fuel cell unit isconnected to the CAE unit of the same fuel cell unit and to the contactplate of an adjacent fuel cell unit via a respective slide fit sealing.

[0086] The same or functionally equivalent elements are designated inall the Figures with the same reference numerals.

[0087] A fuel cell device illustrated in FIGS. 1 to 8 and designated asa whole as 100 comprises an essentially parallelepiped housing 102 (cf.FIG. 1), into which a supply line 104 for oxidation agent opens, viawhich an oxidation agent, for example, air or pure oxygen is supplied tothe interior of the housing 102 by a supply blower (not illustrated) atan overpressure of, for example, approximately 50 millibars.

[0088] Furthermore, a discharge line 105 for oxidation agent, throughwhich superfluous oxidation agent can be discharged from the interior ofthe housing 102, opens into the housing 102.

[0089] A composite block of fuel cells 106 illustrated as a whole inFIG. 2 is arranged in the interior of the housing 102 and comprises alower end plate 108, an upper end plate 110 and a plurality of fuel cellunits 114 which are arranged between the lower end plate 108 and theupper end plate 100 and follow one another along a stacking direction112.

[0090] As is best apparent from FIG. 4, which shows a perspective,exploded illustration of two fuel cell units 114 following one anotheralong the stacking direction 112, each of the fuel cell units 114comprises an essentially plate-like cathode-anode-electrolyte unit 116(abbreviated in the following to: CAE unit) which is held between acontact plate 118 and a fluid guiding frame 120.

[0091] The CAE unit 116 comprises, as illustrated purely schematicallyin FIG. 3, a gas-permeable, electrically conductive support layer 121which can be designed, for example, as a mesh or net consisting of ametallic material, e.g. of nickel, through the openings in which acombustible gas can pass from a chamber 124 for combustible gasadjoining the support layer 121.

[0092] Furthermore, the CAE unit 116 comprises a plate-like anode 122which is arranged on the support layer 121 and consists of anelectrically conductive, ceramic material, such as, for example, Ni-ZrO₂ceramet (ceramic-metal mixture), which is porous in order to enable thecombustible gas from the chamber 124 for combustible gas to pass throughthe anode 122 to the electrolyte 126 adjoining the anode 122.

[0093] A hydrocarbonaceous gas mixture or pure hydrogen can be used, forexample, as combustible gas.

[0094] The electrolyte 126 is preferably designed as a solid electrolyteand formed, for example, from a yttrium-stabilized circonium dioxide.

[0095] On the side of the electrolyte 126 located opposite the anode 122a plate-like cathode 128 borders thereon, which is formed from anelectrically conductive, ceramic material, for example, from LaMnO₃ andhas a porosity in order to enable an oxidation agent, for example, airor pure oxygen to pass to the electrolyte 126 from a chamber 130 foroxidation agent adjoining the cathode 128.

[0096] During operation of the fuel cell device 100 the CAE unit 116 ofeach fuel cell unit 114 has a temperature of, for example, approximately850° C., at which the electrolyte 126 is conductive for oxygen ions. Theoxidation agent from the chamber 130 for oxidation agent absorbselectrons at the anode 122 and releases bivalent oxygen ions to theelectrolyte 126 which migrate through the electrolyte 126 to the anode122. At the anode 122, the combustible gas from the chamber 124 forcombustible gas is oxidized by the oxygen ions from the electrolyte 126and thereby releases electrons to the anode 122.

[0097] The contact plates 118 serve to draw off from the anode 122 viathe support layer 121 the electrons released during the reaction at theanode 122 or rather feed to the cathode 128 the electrons required forthe reaction at the cathode 128.

[0098] For this purpose, each of the contact plates 118 consists of ametal sheet which is a good electrical conductor and is provided (asbest seen from FIG. 5) with a plurality of contact elements 132 whichhave, for example, the shape of projections and recesses which adjoinone another, have a respectively square design and are formed by thesuperposition of a first wave pattern with wave troughs and crestsdirected parallel to the narrow sides 133 of the contact plate 118 and asecond wave pattern with wave troughs and crests directed parallel tothe longitudinal sides 135 of the contact plate 118.

[0099] The contact field 134 of the contact plate 118 formed from thecontact elements 132 thus has the structure of corrugated metalcorruigated in two directions at right angles to one another.

[0100] The contact elements 132 are arranged on the respective contactplate 118 in a square grating, wherein contact elements adjacent to oneanother project alternatingly to different sides of the contact plate118 from the central plane 139 of the contact plate 118. The contactelements on the anode side projecting from the contact plate 118 upwardsand thus to the anode 122 of the CAE unit 116 belonging to the same fuelcell unit 114 are designated with the reference numeral 132 a, thecontact elements on the cathode side projecting from the contact plate118 downwards and thus to the cathode 128 of the CAE unit 116 belongingto an adjacent fuel cell unit 114 are designated with the referencenumeral 132 b.

[0101] The dash-dot lines drawn in in FIG. 5 within the contact field134 reproduce the boundary lines of the contact elements 132, alongwhich the contact plate 118 intersects their central plane 139.

[0102] Each of the contact elements 132 has a central contact area 137,at which it is in electrically conductive contact with an adjoining CAEunit 116.

[0103] The contact areas 137 of the anode-side contact elements 132 a ofa contact plate 118 are in electrical point contact with the supportlayer 121 and thus with the anode 122 of the CAE unit 116 belonging tothe same fuel cell unit 114 so that electrons can pass from therespective anode 122 to the contact plate 118.

[0104] The cathode-side contact elements 132 b of the contact plates 118are in electrically conductive point contact with the cathode 128 of theCAE unit 116 belonging to an adjacent fuel cell unit 114 so thatelectrons can pass from the contact plate 118 to the cathode 128. Inthis way the contact plates 118 make a charge compensation possiblebetween the anodes 122 and cathodes 128 along the stacking direction 112of consecutive CAE units 116.

[0105] The contact plates 118 arranged at the ends of the compositeblock of fuel cells 106 are (in a manner not illustrated in thedrawings) connected to an external current circuit in order to tap theelectrical changes resulting at these edge-side contact plates 118.

[0106] As is best apparent from the plan view of FIG. 5, the central,rectangular contact field 134 of each contact plate 118 provided withthe contact elements 132 is surrounded by a flat flange area 136 whichforms the outer edge of the contact plate 118 and is aligned parallel tothe central plane 139 of the contact field 134 but in relation to thisis displaced towards the CAE unit 116 so that in the area of the narrowlongitudinal sides 138 of the flange area 136 the underside of the CAEunit 116 rests on the upper side of the flange area 136 (cf., inparticular, FIG. 7).

[0107] The broad side areas 140 of the flange area 136 each have a port142 and 144, respectively, which enable the passage of combustible gasto be supplied to the fuel cell units 114 or of waste gas to bedischarged from the fuel cell units 114, this waste gas containingsuperfluous combustible gas and products of combustion, in particular,water.

[0108] The flange area 136 is connected to the contact field 134arranged so as to be offset hereto via an inclined surface 146 whichsurrounds the contact field 134 and adjoins the contact field 134 at afirst bending line 148 and the flange area 136 at a second bending line150.

[0109] Each of the contact plates 118 is designed as a shaped sheetmetal part which is formed from an essentially flat, essentiallyrectangular layer of sheet metal by way of embossing and/or deep drawingas well as by punching or cutting out the ports 142, 144.

[0110] The fluid guiding frames 120 are also formed as shaped sheetmetal parts from an essentially flat, essentially rectangular sheetmetal layer.

[0111] As is best seen in FIG. 6, each fluid guiding frame 120 has atits end areas 152 ports corresponding to the ports 142, 144 in thecontact plates 118, namely a combustible gas port 154 and a waste gasport 156.

[0112] As is best seen from FIGS. 6 and 8, each of the ports 154, 156 ina fluid guiding frame 120 is surrounded by a collar 158 extending alongthe stacking direction 112, a seal contact area 162 adjoining the collar158 along a bending line 160 and extending away from the port at rightangles to the stacking direction 112 and a channel wall area 166adjoining the seal contact area 162 at a bending line 164 and beingaligned parallel to the stacking direction 112. Where the channel wallarea 166 adjoins an outer edge of the frame 120 it merges at a bendingline 167 into a flange area 168 aligned at right angles to the stackingdirection 112.

[0113] As is best seen from FIG. 6, each of the fluid guiding frames 120has between the ports 154, 156 in the end areas 152 of the fluid guidingframe 120 an essentially rectangular, central opening 170 for thepassage of the contact elements 132 of the contact plate 118 of anadjacent fuel cell unit 114.

[0114] As is apparent from FIGS. 6 and 8, the channel wall area 166,where it is adjacent to the opening 170, merges at a bending line 172into an inner edge area 178 of the fluid guiding frame 120 aligned atright angles to the stacking direction 112.

[0115] As is best seen from FIG. 6, the inner edge area 178 of the fluidguiding frame 120 extends all around the opening 170.

[0116] In the narrow longitudinal areas 180 of the fluid guiding frame120, which are arranged between the openings 170 and the outer edge ofthe fluid guiding frame 120 and connect the two end areas 152 of thefluid guiding frame 120 with one another, the inner edge area 178 mergesat its edge facing away from the opening 170 along a bending line 182into a vertical wall area 184 which is aligned parallel to the stackingdirection 112 and, for its part, merges along a bending line 185 intothe flange area 168 forming the outer edge of the fluid guiding frame120.

[0117] As is best seen from FIGS. 4 and 8, each CAE unit 116 is providedat the edge of its upper side facing the fluid guiding frame 120 of thesame fuel cell unit 114 with a gas-tight, electrically insulatingcombustible gas chamber seal 186 which projects laterally beyond the CAEunit 116.

[0118] The combustible gas chamber seal may comprise, for example, aflat seal consisting of mica.

[0119] Alternatively or in addition hereto it may also be provided forthe combustible gas chamber seal 186 to comprise a gas-tight,electrically insulating coating on the underside of the fluid guidingframe 120 which is applied to the underside of the inner edge area 178of the fluid guiding frame 120 by way of the screen printing method orby means of roller coating.

[0120] As is best seen from FIG. 8, the two seal contact areas 162surrounding the ports 154, 156 of the fluid guiding frame 120 areprovided with a respective gas channel seal 188 on their upper sidefacing away from the CAE unit 116.

[0121] The gas channel seal 188 also preferably comprises a flat sealconsisting of mica or a gas-tight, electrically insulating coating whichcan be applied to the seal contact area 162 of the fluid guiding frame120 as a paste by way of the screen printing method or by means ofroller coating.

[0122] In the assembled state of a fuel cell unit 114, the CAE unit 116of the relevant fuel cell unit 114 abuts with its support layer 121 onthe anode-side contact elements 132 a of the contact plate 118 of thefuel cell unit 114.

[0123] The fluid guiding frame 120 of the fuel cell unit 114 abuts, forits part, via the combustible gas chamber seal 186 on the outer edge ofthe cathode 128 of the CAE unit 116 and with the flange area 168 on theflange area 136 of the contact plate 118.

[0124] The flange area 168 and the flange area 136 are secured to oneanother by way of welding (e.g. the laser welding method or the electronbeam method) or by soldering, in particular, a hard soldering and sealedin a gas-tight manner.

[0125] The fuel cell units 114 of the composite block of fuel cells 106are stacked on top of one another along the stacking direction 112 suchthat the cathode-side contact elements 132 b of each contact plate 118extend through the openings 170 in the fluid guiding frame 120 of therespective fuel cell unit 114 arranged therebelow to the cathode of theCAE unit 116 of the fuel cell unit 114 arranged therebelow and abutthereon in electrically conductive contact.

[0126] The flange area 136 of each contact plate 118 thereby abuts onthe gas channel seal 188 of the fluid guiding frame 120 of therespective fuel cell unit 114 arranged therebelow, wherein the collar158, which surrounds the respective port 154 or 156 in the fluid guidingframe 120, extends into the respectively corresponding port 142 or 144of the contact plate 118.

[0127] The end area 152 of each fluid guiding frame 120 surrounding thecombustible gas port 154 forms a combustible gas guiding area. The endarea 152 of each fluid guiding frame 120 surrounding the waste gas port156 forms a waste gas guiding area.

[0128] As is best seen from the sectional illustration of FIG. 2, thecombustible gas guiding areas of the fluid guiding frames 120 whichfollow one another along the stacking direction 112 together form acombustible gas channel 190 which extends parallel to the stackingdirection 112 and at its upper end opens in a recess 192 on theunderside of the upper end plate 110.

[0129] At the lower end of the combustible gas channel 190, acombustible gas supply opening 194 opens into it which passes throughthe lower end plate 108 of the composite block of fuel cells 106coaxially to the combustible gas channel 190.

[0130] A combustible gas supply line 196 is connected to the end of thecombustible gas supply opening 194 facing away from the combustible gaschannel 190, this supply line being guided through the housing 102 ofthe fuel cell device 100 in a gas-tight manner and being connected to acombustible gas supply (not illustrated) which supplies to thecombustible gas supply line 196 a combustible gas, for example, ahydrocarbonaceous gas or pure hydrogen at an overpressure of, forexample, approximately 50 millibars.

[0131] As is likewise best seen from FIG. 2, the waste gas guiding areasof the fluid guiding frames 120 following one another along the stackingdirection 112 together form a waste gas channel 198 which is alignedparallel to the stacking direction 112 and at its lower end is closed bya projection 200 provided on the upper side of the lower end plate 108of the composite block of fuel cells 106.

[0132] At its upper end the waste gas channel 198 opens into a waste gasdischarge opening 202 which is coaxial thereto, passes through the upperend plate 110 of the composite block of fuel cells 106 and at its endfacing away from the waste gas channel 198 is connected to a waste gasdischarge line 204.

[0133] The waste gas discharge line 204 is guided through the housing102 of the fuel cell device 100 in a gas-tight manner and connected to awaste gas treatment unit (not illustrated).

[0134] During operation of the fuel cell device 100 the combustible gasflows through the combustible gas supply line 196 and the combustiblegas supply opening 194 into the combustible gas channel 190 and isdistributed from there through the intermediate spaces between thecontact plates 118 and the respective fluid guiding frames 120 belongingto the same fuel cell unit 114 to the combustible gas chambers 124 ofthe fuel cell units 114 which are each surrounded by the contact plate118, the fluid guiding frame 120 and the CAE unit 116 of the relevantfuel cell unit 114.

[0135] As already described, the combustible gas is oxidized at leastpartially at the anode 122 of the respective CAE unit 116 limiting therespective combustible gas chamber 124.

[0136] The product of oxidation (for example, water) passes togetherwith superfluous combustible gas out of the combustible gas chambers 124of the fuel cell units 114 into the waste gas channel 198, from which itis discharged through the waste gas discharge opening 202 and the wastegas discharge line 204 to the waste gas treatment unit (notillustrated).

[0137] In the waste gas treatment unit, the product of reaction (forexample, water) is, for example, removed from the stream of waste gasand superfluous combustible gas is conducted to the combustible gassupply in order to be supplied again to the fuel cell device 100.

[0138] The oxidation agent required for the operation of the fuel celldevice 100 (for example, air or pure oxygen) is supplied to the interiorof the housing 102 through the oxidation agent supply line 104.

[0139] In the interior of the housing 102, the oxidation agent isdistributed to the oxidation agent chambers 130 which are formed betweenthe combustible gas chambers 124 of the fuel cell units 114 and whichare surrounded by a respective contact plate 118 of a fuel cell unit 114as well as by the fluid guiding frame 120 and the cathode 128 of the CAEunit 116 of an adjacent fuel cell unit 114.

[0140] The oxidation agent passes into the oxidation agent chambers andout of them again by way of the intermediate spaces between a respectivefluid guiding frame 120 of a fuel cell unit 114 and the contact plate118 of the fuel cell unit 114 following thereon in the stackingdirection 112.

[0141] As already described, oxygen ions are formed from the oxidationagent at the cathodes 128 of the CAE units 116 of the fuel cell units114 and these migrate through the electrolytes 126 to the anodes 122 ofthe CAE units 116 of the fuel cell units 114.

[0142] Superfluous oxidation agent passes out of the oxidation agentchambers 130 of the fuel cell units 114 on the exit side locatedopposite the entry side of the oxidation agent and is discharged fromthe interior of the housing 102 of the fuel cell device 100 through theoxidation agent discharge line 105.

[0143] The direction of flow of the combustible gas and the waste gasthrough the fuel cell device 100 is specified in the drawings withsingle arrows 210, the direction of flow of the oxidation agent throughthe fuel cell device 100 by means of double arrows 212.

[0144] The direction of flow of the oxidation agent through theoxidation agent chambers 130 is essentially at right angles to thedirection of flow of the combustible gas through the combustible gaschambers 124.

[0145] In order to secure the fuel cell units 114 following one anotheralong the stacking direction 112 against one another by way of externalclamping, several connecting screws 214 are provided which pass throughbores 216 in the end plates 108, 110 of the composite block of fuelcells 106 and are provided at their end facing away from the respectivescrew head 218 with an external thread 220, into which a respectivecoupling nut 222 is turned so that the end plates 108, 110 are clampedbetween the screw heads 218 and the connecting nuts 222 and a desiredpressing force can be transferred via the end plates 108, 110 onto thestack of fuel cell units 114 (cf. FIG. 2).

[0146] The pressing force generated by the external clamping by means ofthe connecting screws 214 and connecting nuts 222 determines the contactpressure, with which the flange areas 136 of the contact plates 118 arepressed against the gas channel seals 188 on the fluid guiding frames120.

[0147] The contact pressure, with which the fluid guiding frames 120 arepressed against the combustible gas chamber seals 186 on the CAE units116, is, on the other hand,—irrespective of the external clamping bymeans of the connecting screws 214 and connecting nuts 222—determinedexclusively by the elastic biasing force, with which the fluid guidingframe 120 of a fuel cell unit 114 is biased against the CAE unit 116 ofthe same fuel cell unit 114.

[0148] This elastic biasing is generated at the point of time, at whichthe fluid guiding frame 120 and the contact plate 118 of the same fuelcell unit 114 are secured against one another at the flange areas 136and 168, respectively. This elastic biasing force is dependent on thegeometry of the fuel cell units 114 and is brought about due to the factthat the sum of the extensions of a contact element 132 a and the CAEunit 116 with the combustible gas chamber seal 186 arranged thereon inthe stacking direction 112 is somewhat greater than the distance theunderside of the inner edge area 178 of the fluid guiding frame 120would take up from the central plane of the contact field 134 of thecontact plate 118 in the non-deformed state of the fluid guiding frame120. As a result of the CAE unit 116 clamped between the contact plate118 and the fluid guiding frame 120, the fluid guiding frame 120 isdeformed elastically which results in an elastic restoring force whichbiases the fluid guiding frame 120 against the CAE unit 116.

[0149] The composite block of fuel cells 106 described above is mountedas follows:

[0150] First of all, the individual fuel cell units 114 are mounted inthat a CAE unit 116 is arranged each time between a contact plate 118and a fluid guiding frame 120 and, subsequently, the flange areas 136 ofthe contact plate 118 abutting against one another as well as the flangearea 168 of the fluid guiding frame 120 are connected to one another ina gas-tight manner, for example, by welding or soldering, in particular,hard soldering. Subsequently, the composite block of fuel cells 106 isassembled from the individual fuel cell units 114 in that the desirednumber of fuel cell units 114 is stacked along the stacking direction112 and the fuel cell units 114 are fixed in their position relative toone another by means of the end plates 108, 110 and the connectingscrews 214 and connecting nuts 222 bracing the end plates against oneanother.

[0151] A second embodiment of a fuel cell device 100 illustrated in FIG.9 differs from the first embodiment described above in that the contactplates 118 do not merely abut on the fluid guiding frame 120′ of anadjacent fuel cell unit 114 in the area of the gas channel seals 188 butrather are connected to this fluid guiding frame by way of flanging.

[0152] As is apparent from FIG. 9, the collar 158′ of each fluid guidingframe 120′ passes through the waste gas port 144 (or the combustible gasport 142) in the contact plate 118 of the adjacent fuel cell unit 114and merges at a bending line 224 into a flange fold area 226 aligned atright angles to the stacking direction 112.

[0153] The gas channel seal 188′ arranged on the side of the fluidguiding frame 120′ facing the contact plate 118 is designed, in thissecond embodiment, not in one piece as in the first embodiment describedabove but in two pieces and comprises a first flat seal 228, which isarranged between the upper side of the seal contact area 126 of thefluid guiding frame 120′ and the underside of the flange area 136 of thecontact plate 118, and a second flat seal 230 which is arranged betweenthe underside of the flange fold area 226 of the fluid guiding frame120′ and the upper side of the flange area 136 of the contact plate 118.

[0154] The flat seals 228, 230 may be designed as mica seals or asgas-tight, electrically insulating coatings (on the contact plate 118 oron the fluid guiding frame 120′).

[0155] The flange fold area 226 on the fluid guiding frame 120′ forms anundercut, as a result of which the contact plate 118 of the respectivelyadjacent fuel cell unit 114 is secured on the fluid guiding frame 120′.

[0156] In order to reduce the clearance between the contact plate 118and the fluid guiding frame 120′ at right angles to the stackingdirection 112, a spacer ring consisting of an elastically insulating,preferably ceramic material can be arranged in the intermediate spacebetween the edge of the flange area 136 of the contact plate and thecollar 158′ of the fluid guiding frame 120′.

[0157] In this second embodiment, the contact pressure at the gaschannel seal 188′ required for sealing the waste gas channel 198 and thecombustible gas channel 190, respectively, is not first generated by theexternal clamping of the fuel cell units 114 against one another bymeans of the end plates 108, 110 and the connecting screws 214 andconnecting nuts 222 arranged thereon but is already determined duringthe assembly of the stack consisting of fuel cell units 114 due to theflanging of the flange area 136 of each contact plate 118 to the fluidguiding frame 120′ of the adjacent fuel cell unit 114.

[0158] As is apparent from FIG. 9, the inclined surface 146 between thecontact field 134 and the flange area 136 of the contact plate 118 isdispensed with in this second embodiment and so the flange area 136 ofthe contact plate 118 is located approximately at the same level as thecentral plane 139 of the contact plate 118. Furthermore, the channelwall area 166′ of the fluid guiding frame 120′ is not, as in the firstembodiment, aligned parallel to the stacking direction 112 but rather isinclined in relation to the stacking direction 112 through an angle ofapproximately 45°. Moreover, the extension of the channel wall area 166′along the stacking direction 112 is smaller than in the firstembodiment.

[0159] The composite block of fuel cells 106 of the second embodiment ofa fuel cell device 100 is preferably produced in accordance with themethod described in the following:

[0160] First of all, several fluid guiding element-contact plate unitsare preassembled in that a fluid guiding frame 120′ of a fuel cell unit114 is connected each time to the contact plate 118 of an adjacent fuelcell unit by way of flanging in the area of the combustible gas channel190 and the waste gas channel 198.

[0161] Subsequently, a stack consisting of fluid guiding element-contactplate units following one another along the stacking direction 112 isformed, wherein one respective CAE unit is arranged between two suchunits each time such that the cathode 128 of the relevant CAE unit 116abuts on a fluid guiding frame 120′ via the combustible gas chamber seal186.

[0162] Furthermore, the stack consisting of the fluid guidingframe-contact plate units is formed such that each contact plate 118abuts with its flange area 136 on the flange area 168 of the fluidguiding frame 120′ of an adjacent fluid guiding frame-contact plateunit.

[0163] Subsequently, the flange areas 136 of the contact plates 118 areconnected to the flange areas 168 of the respective fluid guiding frames120′ belonging to the same fuel cell unit 114 in a gas-tight manner, forexample, by welding or by soldering, in particular, by hard soldering.

[0164] As for the rest, the second embodiment of a fuel cell devicecorresponds with respect to construction and operation to the firstembodiment and in this respect reference is made to the precedingdescription thereof.

[0165] A third embodiment of a fuel cell device illustrated in FIG. 10differs from the second embodiment described above in that the holdingplates do not merely abut on the CAE units 116 in the area of thecombustible gas chamber seal 186 but rather are connected to these CAEunits 116 by way of flanging.

[0166] As is apparent from FIG. 10, in this embodiment a contact area236 aligned at right angles to the stacking direction 112 adjoins theseal contact area 126 of the fluid guiding frame 120′ along a bendingline 234, this contact area abutting with its upper side areally on theunderside of the seal contact area 126 and, for its part, merging at abending line 238 into a channel wall area 166 aligned parallel to thestacking direction 112.

[0167] A flange fold area 240 adjoins the lower edge of the channel wallarea 166 along a bending line 238, is aligned at right angles to thestacking direction 112 and abuts with its upper side on the underside ofthe support layer 121 of the CAE unit 116.

[0168] The flange fold area 240 on the fluid guiding frame 120′ forms anundercut, as a result of which the CAE unit 116 is secured on the fluidguiding frame 120′ of the same fuel cell unit 114.

[0169] In this third embodiment, the contact pressure at the combustiblegas chamber seal 186 required for sealing the combustible gas chamber124 is not—as in the first two embodiments—determined by the relativeextensions of the contact elements 132 and the fluid guiding frame alongthe stacking direction 112 but is generated directly as a result of theflanging about the CAE unit 118 by the fluid guiding frame 120′.

[0170] As for the rest, the third embodiment of a fuel cell devicecorresponds with respect to construction and operation to the secondembodiment and in this respect reference is made to its descriptionabove.

[0171] A fourth embodiment of a fuel cell device illustrated in FIG. 11differs from the first embodiment described above in that the gaschannel seal is not designed in the fourth embodiment—as in the firstembodiment—as a flat seal acted upon with an external clamping force butrather as a slide fit sealing.

[0172] As is apparent from the sectional illustration of FIG. 11, thechannel wall area 166 of the fluid guiding frame of the first embodimentwhich is aligned parallel to the stacking direction 112 is omitted inthe case of the fluid guiding frame 120″ of the fourth embodiment and soin the fourth embodiment the inner edge area 178 of the fluid guidingframe 120″ merges directly into the seal contact area 162 of the fluidguiding frame 120″ without any bending line. The seal contact area 162merges at its edge facing away from the inner edge area 178 along abending line 242 into a channel wall area 244 which is aligned parallelto the stacking direction 112 and, on the other hand, merges at itsupper edge facing away from the seal contact area 162 along a bendingline 246 into a shoulder area 248 which is aligned essentially at rightangles to the stacking direction 112 and is directed into the respectiveport 154 or 156.

[0173] The contact plate 118′ has in this fourth embodiment, in contrastto the contact plate of the first embodiment, at each of the ports 142and 144 a collar 250 which surrounds the relevant port in a ring shape,is aligned essentially parallel to the stacking direction 112 andborders along a bending line. 252 on the respectively adjacent inclinedsurface 146 and the flange area 136 of the contact plate 118′,respectively.

[0174] As is apparent from FIG. 11, a respective spacer element 252surrounding the channel wall area 244 in a ring shape is arranged on theupper side of the seal contact area 162 and on the outer side of thechannel wall area 244 of each fluid guiding frame 120″, this spacerelement having an essentially L-shaped cross section with a first arm254, which rests on the seal contact area 162 and is aligned essentiallyat right angles to the stacking direction 112, and with a second arm 256which rests on the outer side of the channel wall area 244 and isaligned essentially parallel to the stacking direction 112.

[0175] The first arm 254 of the spacer element 252 serves as a distancepiece between the collar 250 of the contact plate 118′ and the sealcontact area 162 of the holding plate 120″.

[0176] The second arm 256 of the spacer element 252 serves as a distancepiece between the collar 250 of the contact plate 118′ and the channelwall area 244 of the fluid guiding frame 120″.

[0177] The spacer element 252 consists of an electrically insulatingmaterial which is rigid and resistant at the operating temperature ofthe fuel cell device 100 of, for example, approximately 850° C.

[0178] The spacer element 252 can, for example, be formed from Al₂O₃.

[0179] The second arm 256 of the spacer element 252 supports a sealingbead 256 which surrounds the channel wall area 244 of the fluid guidingframe 120″ in a ring shape and closes the gap between the channel wallarea 244 and the collar 250 of the contact plate 118′.

[0180] The sealing bead 258 consists of an electrically non-conductivematerial which is viscous but chemically resistant at the operatingtemperature of the fuel cell device 100 of, for example, approximately850° C.

[0181] A solder glass or an amorphous material similar to glass can be;considered, in particular, as material for the sealing bead 256.

[0182] If the sealing bead 258 is formed from a solder glass, it can beproduced by applying a paste containing powdered glass.

[0183] When the operating temperature of the fuel cell device 100 isreached, the melted sealing bead 258 fills the gap between the collar250 of the contact plate 118′ and the channel wall area 244 of the fluidguiding frame 120″ in a gas-tight manner.

[0184] Possible differences in pressure between the combustible gaschamber 124 and the oxidation agent chamber 130 or different heatexpansions are compensated by a displacement of the collar 250 of thecontact plate 118′ relative to the fluid guiding frame 120″.

[0185] This is possible without more ado since the contact plate 118′and the fluid guiding frame 120″ are, in this embodiment, not rigidlyconnected to one another but rather the collar 250 of the contact plate118′ and the holding plate 120″ are displaceable relative to one anotheralong the stacking direction 112, namely by the distance, by which thesecond arm 256 of the spacer element 252 projects beyond its first arm254 along the stacking direction 112. If the collar 250 is displacedrelative to the fluid guiding frame 120″ proceeding from the initialposition illustrated in FIG. 11 along the stacking direction 112upwards, the melted sealing bead 258 continues to provide for agas-tight sealing between the contact plate 118′ and the fluid guidingframe 120″ while the spacer element 252 prevents the viscous mass of thesealing bead 258 from running out into the oxidation agent chamber 130.

[0186] The contact plate 118′ and the fluid guiding frame 120″ are alsodisplaceable relative to one another at right angles to the stackingdirection 112, namely by the distance, by which the first arm 254 of thespacer element 252 projects beyond its second arm 256 at right angles tothe stacking direction 112. If the collar 250 is displaced relative tothe fluid guiding frame 120″ proceeding from the initial positionillustrated in FIG. 11 at right angles to the stacking direction 112,the melted sealing bead 258 continues to provide for a gas-tight sealingbetween the contact plate 118′ and the fluid guiding frame 120″.

[0187] Such a slide fit sealing at the combustible gas channel 190 andthe waste gas channel 198 is particularly suitable for compensating fordifferences between the individual components of the fuel cell units 114(CAE unit 116, contact plate 118′ and fluid guiding frame 120″) withrespect to their thermal coefficients of expansion.

[0188] Since no predetermined contact pressure is required for the slidefit sealing, it is also not-necessary with this fourth embodiment—in thesame way as with the second and the third embodiments—to brace the fuelcell units 114 of the composite block of fuel cells 106 against oneanother. It is merely necessary for the fuel cell units to be fixed intheir position relative to one another and for an adequate contactpressure to be generated between the CAE units and the contact plates.

[0189] To produce the composite block of fuel cells 106 of the fourthembodiment the procedure is preferably—as with the first embodiment—suchthat first of all the individual fuel cell units 114 are connected toone another by way of a gas-tight connection of the contact plate 118′and the fluid guiding frame 120″ of the same fuel cell unit 114 and,subsequently, the assembled fuel cell units 114 are stacked on top ofone another along the stacking direction 112.

[0190] As for the rest, the fourth embodiment of a fuel cell devicecorresponds with respect to construction and operation to the firstembodiment and in this respect reference is made to its descriptionabove.

[0191] A fifth embodiment of a fuel cell device illustrated in FIG. 12differs from the fourth embodiment described above in that apart fromthe gas channel seal 188″ in the fourth embodiment the combustible gaschamber seal 186′ is also designed as a slide fit sealing.

[0192] As is apparent from the sectional illustration of FIG. 12, asloping wall area 262, which is inclined at an angle of approximately45° in relation to the stacking direction 112 and merges into a wallarea 266 curved in an S shape along a bending line 264 at its lower edgefacing away from the seal contact area 162, borders on the seal contactarea 162 along a bending line 260 in the case of the fluid guiding frame120″ of the fifth embodiment. The wall area 266 curved in an S shapeborders, for its part, at its upper edge facing away from the slopingwall area 262 on the inner edge area 178 of the fluid guiding frame120″.

[0193] As is apparent from FIG. 12, a respective spacer element 270surrounding the CAE unit 116 in a ring shape is arranged on theunderside of the inner edge area 178 and on the side wall 268 of the CAEunit 116, this spacer element having an essentially L-shaped crosssection with a first arm 272, which abuts on the side wall 268 of theCAE unit 116 and is aligned essentially parallel to the stackingdirection 112, and with a second arm 274 which abuts on the upper sideof the CAE unit 116 and on the underside of the inner edge area 178 ofthe fluid guiding frame 120″ and is aligned essentially at right anglesto the stacking direction 112.

[0194] The first arm 272 of the spacer element 270 serves as a distancepiece between the CAE unit 116 and the curved wall area 266 of the fluidguiding frame 120″. The second arm 274 of the spacer element 270 servesas a distance piece between the CAE element 116 and the inner edge area178 of the fluid guiding frame 120″.

[0195] The distance element 270 also consists of an electricallyinsulating material which is rigid and resistant at the operatingtemperature of the fuel cell device 100 of, for example, approximately850° C., for example, of Al₂O₃.

[0196] A sealing element 276 closed in a ring shape is arranged alongthe inner edge of the second arm 274 of the spacer element 270 andconsists of an electrically non-conductive material which is viscous butchemically resistant at the operating temperature of the fuel celldevice 100 of, for example, approximately 850° C.

[0197] A solder glass or an amorphous material similar to glass can beconsidered, in particular, as material for the sealing element 276.

[0198] If the sealing element 276 is formed from a solder glass, it maybe produced by applying a paste containing powdered glass to the upperside of the CAE element 116, for example, with the screen printingmethod.

[0199] Once the operating temperature of the fuel cell device 100 isreached, the melted sealing element 276 fills the entire intermediatespace between the inner edge area 178 of the fluid guiding frame 120″and the CAE element 116 in a gas-tight manner.

[0200] Possible differences in pressure between the combustible gaschamber 124 and the oxidation agent chamber 130 or differences withrespect to the heat expansion of the individual components of the fuelcell units 114 are compensated by a relative displacement between theCAE unit 116 and the fluid guiding frame 120″.

[0201] This is possible without further ado since the CAE unit 116 andthe fluid guiding frame 120″ are not rigidly connected to one anotherbut are displaceable relative to one another at right angles to thestacking direction 112, namely by the distance, by which the second arm274 of the spacer element 270 projects beyond its first arm 272 at rightangles to the stacking direction 112.

[0202] If the CAE unit 116 is displaced relative to the fluid guidingframe 120″ proceeding from the initial position illustrated in FIG. 12at right angles to the stacking direction 112 to the left, the meltedsealing element 276 continues to provide for a gas-tight sealing betweenthe CAE unit 116 and the fluid guiding frame 120″ while the spacerelement 270 prevents the viscous mass of the sealing element 276 fromrunning out into the combustible gas chamber 124.

[0203] Such a slide fit sealing between the combustible gas chamber 124and the oxidation agent chamber 130 is particularly suitable forcompensating for any difference between the individual components of thefuel cell units 114 (CAE unit 116, contact plate 118′ and fluid guidingframe 120″) with respect to their thermal coefficients of expansion.

[0204] As for the rest, the fifth embodiment of a fuel cell devicecorresponds with respect to construction and operation to the fourthembodiment and in this respect reference is made to its descriptionabove.

1. Fuel cell unit, comprising a cathode-anode-electrolyte unit and acontact plate in electrically conductive contact with thecathode-anode-electrolyte unit, wherein the fuel cell unit comprises afluid guiding element connected to the contact plate in a fluid-tightmanner, forming a boundary of a fluid chamber having fluid flowingthrough it during operation of the fuel cell unit and being formed as ashaped sheet metal part.
 2. Fuel cell unit as defined in claim 1,wherein the cathode-anode-electrolyte unit is arranged on the fluidguiding element, preferably held between the fluid guiding element andthe contact plate.
 3. Fuel cell unit as defined in claim 1, wherein thecontact plate is designed as a shaped sheet metal part.
 4. Fuel cellunit as defined in claim 1, wherein the fluid guiding element and thecontact plate are connected to one another by way of welding, preferablyby laser welding or by electron beam welding, or by way of soldering,preferably by hard soldering.
 5. Fuel cell unit as defined in claim 1,wherein the fluid guiding element has an opening for the passage ofcontact elements to the cathode-anode-electrolyte unit.
 6. Fuel cellunit as defined in claim 1, wherein the fluid guiding element abuts onthe cathode-anode-electrolyte unit via an electrically insulating seal.7. Fuel cell unit as defined in claim 6, wherein the seal comprisesmica.
 8. Fuel cell unit as defined in claim 6, wherein the sealcomprises a flat seal.
 9. Fuel cell unit as defined in claim 6, whereinthe seal comprises a coating on the fluid guiding element and/or on thecathode-anode-electrolyte unit.
 10. Fuel cell unit as defined in claim1, wherein the cathode-anode-electrolyte unit and the fluid guidingelement are biased elastically against one another.
 11. Fuel cell unitas defined in claim 1, wherein the fluid guiding element is providedwith at least one fluid port.
 12. Fuel cell unit as defined in claim 11,wherein the fluid guiding element is provided with a fluid supplychannel opening and with a fluid discharge channel opening.
 13. Fuelcell unit as defined in claim 1, wherein the fuel cell unit comprises anelectrically insulating fluid channel seal, the contact plate of thefuel cell unit abutting on the fluid guiding element of an adjacent fuelcell unit via said seal.
 14. Fuel cell unit as defined in claim 1,wherein the fuel cell unit comprises a fluid channel seal, the fluidguiding element of the fuel cell unit abutting on the contact plate ofan adjacent fuel cell unit via said seal.
 15. Fuel cell unit as definedin claim 14, wherein the fluid channel seal comprises a coating on thefluid guiding element and/or on the contact plate.
 16. Fuel cell unit asdefined in claim 14, wherein the fluid channel seal comprises a flatseal.
 17. Fuel cell unit as defined in claim 14, wherein the fluidchannel seal comprises at least two separate sealing elements.
 18. Fuelcell unit as defined in claim 14, wherein the fluid channel sealcomprises a slide fit sealing.
 19. Fuel cell unit as defined in claim14, wherein the fluid channel seal comprises a material, preferably asolder glass, viscous at the operating temperature of the fuel cellunit.
 20. Composite block of fuel cells, comprising a plurality of fuelcell units as defined in claim 1, said units following one another alonga stacking direction.
 21. Composite block of fuel cells as defined inclaim 20, wherein the composite block of fuel cells comprises at leastone clamping element for bracing the fuel cell units against oneanother.
 22. Composite block of fuel cells as defined in claim 21,wherein the composite block of fuel cells comprises two end platesadapted to be braced against one another by means of the clampingelement.
 23. Composite block of fuel cells as defined in claim 22,wherein at least one of the end plates has at least one fluid port. 24.Composite block of fuel cells as defined in claim 20, wherein the fluidguiding element of at least one of the fuel cell units is connected tothe contact plate of an adjacent fuel cell unit by way of flanging. 25.Composite block of fuel cells as defined in claim 24, wherein a flangefold area engaging around the contact plate of the adjacent fuel cellunit is formed on the fluid guiding element of at least one of the fuelcell units.
 26. Composite block of fuel cells as defined in claim 25,wherein an electrically insulating fluid channel seal is arrangedbetween the flange fold area and the contact plate of the adjacent fuelcell unit.
 27. Method for manufacturing a composite block of fuel cellshaving a plurality of fuel cell units as defined in claim 1, comprisingthe following method steps: Assembly of the individual fuel cell unitsby arranging a cathode-anode-electrolyte unit between a contact plateand a fluid guiding element and fluid-tight connection of the contactplate to the fluid guiding element; subsequent assembly of the compositeblock of fuel cells by arranging a plurality of fuel cell units along astacking direction and fixing the fuel cell units in their positionrelative to one another.
 28. Method as defined in claim 27, wherein thefuel cell units of the composite block of fuel cells are braced againstone another by at least one clamping element.
 29. Method as defined inclaim 28, wherein the fuel cell units of the composite block of fuelcells are arranged between two end plates and the two end plates arebraced against one another.
 30. Method as defined in claim 1, whereinthe fluid guiding element of at least one fuel cell unit abuts on thecontact plate of an adjacent fuel cell unit via a flat seal or a slidefit sealing.
 31. Method for manufacturing a composite block of fuelcells having a plurality of fuel cell units as defined in claim 1,comprising the following method steps: Assembly of several fluid guidingelement-contact plate units by connecting a respective fluid guidingelement of one fuel cell unit to a contact plate of an adjacent fuelcell unit by way of flanging; formation of a stack consisting of fluidguiding element-contact plate units following one another along astacking direction, wherein one respective cathode-anode-electrolyteunit is arranged between two such respective units; fluid-tightconnection of the contact plates of the fuel cell units to therespective fluid guiding element of the same fuel cell unit.